A goal by Joe Ledley on the half-hour was enough to make it three wins and a draw over the holiday period but Cardiff had to battle hard to beat Plymouth 1-0.
Jimmy Floyd Hasselbaink won a tackle in a central position before finding Tony Capaldi down the left flank.
The former Argyle defender cut inside and his shot was beaten away by Romain Larrieu only for Ledley to follow up and side foot into the empty net.
"It was a battle throughout the game but we kept going," said Cardiff manager Dave Jones who watched the match from the stands after being given a two-match suspension.
"In the second half it looked like two very tired teams out there and although we missed a couple of chances late, on we stuck to the task.
"It was a very important game to win today as they are a very good side and now we need the break from league football as there are a lot of tired bodies in the dressing room."
City began full of confidence after a string of good results had seen them move up to mid-table.
Argyle showed why they are in among the play-off contenders by putting the home defence under pressure and Kasper Schmeichel had to make a couple of timely stops to keep the visitors out.
A loose header by Roger Johnson in the 18th minute went straight to Argyle's Lee Martin and he crashed in a shot that whistled past an upright.
In another sortie, Peter Halmosi lifted a shot over the crossbar when well placed.
The decisive breakthrough came in the 29th minute but Paul Sturrock's side almost replied straight away when David Norris's shot took a deflection to wrong-foot Schmeichel before flashing just past the post.
In the 33rd minute a brave diving header by Johnson ended with him leaving the field for treatment to a mouth injury.
While the Bluebirds were down to 10 men, they were forced back on the defensive and it was a great relief to home fans when Johnson returned down the tunnel.
The second half continued as the first with City's front men unable to hold on to the ball and it was no surprise when the ineffective Hasselbaink was withdrawn in the 62nd minute to be replaced by Steve MacLean .
But it was MacLean who wasted two glorious chances to put the result beyond doubt after Ledley had produced defence-splitting passes.
His first attempt went straight at Larrieu and then he blasted his second opportunity well wide.
"It seemed to be a game too far for some of my players," said disappointed Argyle boss Paul Sturrock.
"Cardiff started well, scored the goal and it turned out to be difficult for us chasing the game as it seemed to sap our strength.
"Everybody seems able to beat everyone else in this division and if I can dabble in the transfer market we can maybe freshen things up as we need more competition for places.
"It is a very difficult division and my aim is to stay in the race for the play offs until I can strengthen."
The Christmas period has proved to be a good one for the Bluebirds as instead of looking at a relegation fight they are now genuine contenders for one of the play off positions.
Cardiff (4-4-2): Schmeichel; McNaughton, Loovens, Johnson, Capaldi; Whittingham (Thompson 71), McPhail, Rae, Ledley; Parry, Hasselbaink (MacLean 62). Substitutes not used: Oakes (gk), Purse, Blake.
Plymouth (4-4-2): Larrieu; Connolly, Timar (Doumbe 56), Seip, Hodges; Martin (Nalis 56), Nadjim (Jutkiewicz 75), Norris, Halmosi; Easter, Ebanks-Blake. Substitutes not used: McCormick (gk), Summerfield.
Referee: A Whiley (Staffordshire).Reuse content